PURPOSE: To maintain the washing power in the method of operating a dishwasher by improving the deterioration of the painted tableware such as bottle for juicy substance and the high class glass tableware, which is caused by the high temperature of washing water in the true washing process and the final rinsing process.

CONSTITUTION: Since each washing water temperature in the preparatory washing process, true washing process, and the rinsing processes in plural times is raised to a range below the temperature which gives a large effect on the deterioration of tableware, the deterioration of the painted tableware such as a bottle for juicy substance and the high class glass tableware can be prevented. Further, since the washing water temperature in the final rinsing process is raised to the temperature higher than that in the preparatory washing process, true washing process, and the rinsing processes other than the final rinsing process, the oily dirt which is left up to the final rinsing process can be dissolved and can be discharged outside a washing tub.